1. Field
One embodiment of the present invention relates to an electronic device, for example, which contains a printed circuit board in which soldered jointed portions of parts mounted on a surface of the board are reinforced with an adhesive.
2. Description of the Related Art
Electronic devices such as personal computers employ surface mount parts, for example, a ball grid array (BGA) in order to increase the package density of the printed circuit board. In the case where surface mount parts of this type are mounted on a printed circuit board, a coating agent or the like is applied on surface mount parts and the printed circuit board to be across over them in some cases for the protection of the jointed parts as discussed in Jpn. Pat. Appln. KOKAI Publication No. 4-122053.
In order to reinforce a solder jointed portion between a surface mount portion and a printed circuit board, which is weak to a stress caused by impulse, for example, a thermosetting adhesive is used. The adhesive is supplied to the outer circumferential edge of the surface mount part and the printed circuit board to be across over them, and then cured. In this matter, the adhesive reinforces the solder joint between the surface mount part and the printed circuit board, and thus the disconnection of the solder joint can be prevented.
In some cases, a surface mount part such as BGA is mounted on a substrate in such a state where a chip, which generates heat, is exposed. In order to cool down such a chip, a cooling mechanism such as a heat sink is provided for the surface mount part, and thus the part is thermally connected to the chip. The cooling mechanism is positioned to have a gap between the chip and itself. This gap is then filled with a grease having a heat conductivity.
If inclined or brought into direct contact with a chip, the cooling mechanism may damage the chip. In order to avoid this, a spacer is provided for the substrate of the surface mount part in order to maintain the gap between the cooling mechanism and the chip. The spacer is, for example, a rectangular-shaped part formed of a resin. The spacer maintains the gap between the cooling mechanism and the chip appropriately, and thus prevents the chip from being damaged due to the inclining of or direct contact by the cooling mechanism.
However, at the same time, it requires the excessive work to mount the spacer to the substrate of the surface mount part. Further, the spacer is required although it is not directly related to the performance of the surface mount part, and thus the number of parts is increased, which causes a higher production cost of the electronic device.